The invention relates to an energy saving protected roof system which reduces cooling costs and extends roof life expectancy over conventional roofing through the use of a waterproof surface located below interlocking insulation panels constrained between structural edges with drains located beneath the insulation panels. In a preferred embodiment, the panels float on a water reservoir contained by the waterproof surface with the water cooled by circulation above the insulation panels at night.
Conventional roofing for commercial and industrial buildings (see FIG. 1) usually consists of a roof deck 10 covered by a layer of insulation 12 followed by a waterproof membrane 14 and an exterior surface, usually gravel 16. Conventional roofing suffers many inherent problems. Solar radiation can heat a roof surface up to 180.degree. F. which when coupled with nighttime temperatures that can range to below 0.degree. F., subject a conventional roof to extreme temperature change cycles which can shrink, expand, soften or harden roofing, thereby seriously degrading roofing structures over time. Additionally, rain can cause frequent wet/dry cycles on the roofing structure and wind can cause surface erosion and other deterioration of the roof structure by blowing sharp objects against the roof membrane. Further, conventional roofing suffers many problems involving undesirable heat transfer in that the interior of the structure becomes hot due to high roof temperatures or cold due to heat loss through the roof.
Protected membrane roofs (PMR's) have been developed to extend the life of roof membranes via placement below an insulation layer, protecting the membrane from sunlight and extreme temperature changes. For example, the Dow Chemical Co. has developed an inverted roof membrane application (IRMA and insulating panels (see U.S. Pat. Nos. 3,411,256; 4,054,691; 4,067,164; and 4,739,599). PMR's use rigid insulation panels which will not absorb moisture, maintaining their insulating properties even in wet weather. The insulating panels are typically ballasted with gravel or an integral layer of concrete. The ballast protects the panel plastic foam material from ultraviolet degradation, and resists wind uplift. PMR's have not been widely successful due to high costs related to ballasting the panels and providing additional restraints against wind uplift. PMR's also fail to prevent wet/dry cycling which contributes to membrane degradation.
The prior art also describes certain insulation materials and constructions to reduce cooling and heating costs of a building through the use of a liquid medium directly located on a building structure which can be heated or cooled through solar radiation and other means. For example, U.S. Pat. Nos. 3,450,192 and 3,563,305, both Hay, disclose processes and apparatus for modulating the temperature within a water-jacketed enclosure.
U.S. Pat. Nos. 3,994,278 and 4,082,080, both to Pittinger, discloses heating and cooling systems which utilize energy as an energy source and a fluid body as a storage medium. The fluid body is distributed over the roof of a dwelling and includes mechanisms for regulating the temperature within the enclosed structure.
However, all four of the referenced patents "closed" water containment systems are designed primarily for solar heating. The water containment systems are placed on a primary roof membrane for thermal storage containment.
The prior art references have some disadvantages which have not been overcome. Firstly, since a closed liquid system is used, optimum cooling efficiency cannot be obtained since no evaporative cooling can be accomplished. Secondly, the references fail to provide an improved roofing exterior with respect to longevity, durability, etc. The plastic or glass cover provides minimal protection from the elements such as severe wind storms, hail, heavy rains, fallen debris, etc.